1. Field of the Invention
The invention relates to an apparatus for determining the density of liquids and gases from the length of a period of an oscillator filled with a test sample, an oscillation amplifier being provided for its excitation which excites the oscillator in its mechanical resonance frequency via electromechanical transducers and which emits a periodic electrical signal, the period of which corresponds with the period of the oscillator or a multiple thereof.
2. Description of the Related Art
Such an apparatus was disclosed, for example, in Austrian Letters Patent 356,943. In this known apparatus, transducers consisting of coils and permanent magnets are attached to the oscillator at locations with broad amplitudes. The oscillator is particularly sensitive in regard to density changes of the test sample at these locations. These locations are also particularly sensitive to temperature because of the thermal expansion coefficient of the test sample. The self-heating of a coil caused by its excitation current therefore is a source of errors in connection with highly accurate density measurements.